1. Technical Field of the Invention
The present invention relates to a chemically amplified resist comprising a base resin and a photoacid generator and, more particularly, to a far-ultraviolet resist which provides excellent adhesion to Si substrates, improved resistance to dragging and placement after exposure, and improved pattern shapes.
2. Description of the Related Art
Conventional far-ultraviolet resists comprising a base resin and a photoacid generator include, as said base resin, a resin (t-butyl protective poly-carboxyl nor-bornane) with a cyclic carbonate employed, high in transparency to the far ultraviolet radiation, excellent in resistance to etching, and captured in the principal chain to allow a carbon atom--carbon atom bond as shown by formula (1) below. ##STR1##
In addition, conventional far-ultraviolet resists comprising a base resin and a photoacid generator also include a resin (tetra-hydroxyl protective carboxy tetra-cyclo dodecyl-methacrylate) which is branched from the principal chain as shown by formula (2) below. ##STR2##
Conventional far-ultraviolet resists have mainly employed these resins.
However, the aforementioned conventional far-ultraviolet resists provide inferior adhesion to Si substrates and provide deformed patterns when employed in fine patterns or defocused. Moreover, some of these conventional far-ultraviolet resists cannot be developed with a 2.38% TMAH standard developer, presenting a problem in that the resists are used with difficulty in practice.
Furthermore, a conventional KrF (.lambda.=248 nm) resist that employs hydroxystyrene as the base resin and is comparatively good in resistance to etching cannot be used for lithography in which ArF (.lambda.=193 nm) or a far-ultraviolet radiation shorter in wavelength than that which is used, because of significant absorption thereof. Accordingly, a resist with an alicyclic group is now used, however, this resist provides significant hydrophobicity, thus leading to a drawback of inferior adhesion between the resist and the substrate. Moreover, introduction of a unit for improving the adhesion would cause the ratio of the alicyclic group to decrease and thus the resistance to etching to deteriorate, so that both adhesion and resistance to etching have conventionally been satisfied with difficulty at the same time.